<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <script>
        //   var reg = /a*/;
        //   var str = "xgws";
        //   console.log(reg.test(str));

        //   var reg = /a+/;
        //   var str = "azaxacaab";
        //   console.log(reg.test(str));

        //   var reg = /ba?c/;
        //   var str = "gkkfh";
        //   console.log(reg.test(str));

      //   var reg = /ab{2}/;
      //   var str = "aabcbdfb";
      //   console.log(reg.test(str));

      var reg=/ab{2,4}/
      var
    </script>
  </body>
</html>
